The present invention relates to an optical information recording medium wherein information can be recorded and reproduced by making use of a laser beam, and more particularly to an optical information recording medium comprising a primer coating layer formed on a glass base and formed on said primer coating layer a recording layer capable of recording and reproducing information through the use of a laser beam.
In the so-called "direct-read-after-write recording medium" wherein information is recorded by taking advantage of an irreversible change in the characteristics or geometry, a low-melting metal, such as tellurium or bismuth, and its alloy, compound or dispersion have hitherto been used as a recording layer.
A disk, card, etc. provided with or without a guide groove and made of a plastic such as a polycarbonate resin or an acrylic resin have come to be used as a base serving as a support of a recording layer. A glass base, particularly a disk-shaped base has been used in applications particularly where reliability is required, such as computer applications, or applications in an environment susceptible to vibration, such as in an aircraft. The glass base is classified into one having a guide groove formed by the so-called 2 P process which comprises providing on a glass plate a thin layer of a photocurable resin in an uncured state, transferring a guide groove from a stamper and photocuring the resin, and a guide groove-free glass base. The latter has a drawback that when a recording layer of a low-melting metal, such as tellurium or bismuth, and its alloy, compound, etc. is directly provided on a glass base, the recording sensitivity during recording by a laser beam is lower than that in the case where a plastic base and a glass plate having a guide groove formed by the above-described 2 P process are used.
For this reason, an attempt to improve the sensitivity has been made through provision of some primer coating layer on a glass base and provision of a recording layer thereon. An improvement in the recording sensitivity can be attained when an organic polymer layer is used as the primer coating layer. However, it has been found that the use of the organic polymer layer brings about a problem in the reliability of an optical recording medium due to poor adhesion between the organic polymer layer as the primer coating layer and the glass base.
The present inventors have made various studies on the material for the primer coating layer with a view on solving the above-described problem and, as a result, have found that the use of a layer comprising a certain kind of organic polymer as the primer coating layer improves the adhesion between the undercoating layer and the glass base and brings about an improvement in the recording sensitivity, which has led to the completion of the present invention.